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09/02 '00 WED 17 06 FAX 19259469966 ER "ST WC 0023 <br /> '� PAGE 6 <br /> Summary of Realistic Exposure Pathways <br /> In sununaary, the following exposure pathways were selected for <br /> evaluation in the BRA: <br /> Medium Scenario F4 posnre Roat-e <br /> Soil Construction fi cidental mgeshon <br /> Dermal contact <br /> lnhalat wn of vapors(VOCs only) <br /> Grauand water industrid Ird alahon of valavrs(VOCs only) <br /> Ground water Oanstructivn Inhalation of vap=(VOCs only) <br /> D EVELOPMOY7 OF SITE-SPECLMC SCREENS G LEVELS <br /> Based on the realistic exposure pathways identified in the preceding <br /> simian., flmee sets of risk-based screexung levels were develaped,as <br /> follows <br /> m Rask-based screening levels for soil,based on a comtruction scenario <br /> Risk-based screening levels for ground water,based on an industrial <br /> scenario. <br /> Disk-based screening levels for ground wafter, biased on a construction <br /> scenano. <br /> '!`able 1 presents the risk-based screening levels for soil. These caleulated <br /> levels were developed in accordance with guidance issued by USEPA <br /> (3996), USEPA Region 9 (1999),and ASTM (1.996), and incorporate current <br /> toxiaty information published by California EPA mid USEPA. Exposure <br /> assumptions are based on default values recommended by US]HPA in all <br /> cases,except with regard to exposure frequency and exposure duration. <br /> Default values are not available for these pa;ranv-tern under a construction <br /> scenario,and so site-spec assumptions were made regarding exposure <br /> ��'ei7Rs71/'�T RYI� aYr.neYYro rls,roFYn*+ Trti l,r�ati+n4+1,n�,.r.:N.r.� .,.,.+-. .-•r,••.,•.•••�� <br />